Methods and apparatus for underwater drilling of oil and gas wells

ABSTRACT

An apparatus for use in drilling maintaining and servicing an oil or gas well comprising a sealed chamber supported below the water level but above the sea-bottom on a pile driven into the bottom. A number of well casings having their upper ends within the chamber project into the sea-bed, and their upper ends carry well-head control valves for controlling the oil or gas flow from the well casings. The chamber can be constructed in two parts, namely a bottom or platform part which is attached to the pile after the pile has been driven into the sea-bed and which provides apertures to allow the well casings to be passed through on to the sea-bed and driven, and an upper portion which has an access pipe leading to a point above the surface and which is sealingly secured to the platform part after the wells have been drilled.

United States Patet Downs Dec. 10, 1974 15 1 METHODS AND APPARATUS FOR 3,638,720 2/1972 Thomas l66/.5 UNDERWATER DRILLING OF O AND 3,665,721 5/1972 Wyllie 175/9 X 3,703,207 11/1972 Horton l66/.5

GAS WELLS [76] Inventor: Geoffrey Eke Downs, Lynwood Stokesley Rd., Yarm, England [22] Filed: May 8, 1972 [21] Appl. No.: 251,195

[30] Foreign Application Priority Data May 27, 1971 Great Britain 17676/71 [52] [1.5. CI. 175/5, l66/.5 [51] Int. Cl. E2lb 7/12 [58] Field of Search l66/.5, 16; 175/8, 9, 7

[56] References Cited UNITED STATES PATENTS 2,187,871 l/l940 Voorhees 175/8 2,756,021 7/1956 Townsend et al.. 175/8 2,854,215 9/1958 Cox l66/.5 2,906,500 9/1959 Knapp et a]. l66/.5 3,372,745 3/1968 Holmes l66/.6 3,525,388 8/1970 Mcclintocku. l66/.5

3,552,903 l/1966 Townsend l66/.5 3,556,210 1/1971 Johnson 175/7 X 3,601,189 8/1971 Weiss r. 166/5 Primary Examiner-Frank L. Abbott Assistant Examiner-Richard E. Favreau Attorney, Agent, or Firm-Wenderoth, Lind & Ponack ABSTRACT An apparatus for use in drilling maintaining and servicing an oil or gas well comprising a sealed chamber supported below the water level but above the seabottom on a pile driven into the bottom. A number of well casings having their upper ends within the chamber project into the sea-bed, and their upper ends carry well-head control valves for controlling the oil or gas flow from the well casings. The chamber can be constructed in two parts, namely a bottom or platform part which is attached to the pile after the pile has been driven into the sea-bed and which provides apertures to allow the well casings to be passed through on to the sea-bed and driven, and an upper portion which has an access pipe leading to a point above the surface and which is sealingly secured to the platform part after the wells have been drilled.

1 Claim, 3 Drawing Figures PATENTEI HEB I DISH SHEET 1 OF 3 Hal.

PAIENTE 3:2 1 0 1974 SHEET 2 0F 3 METHODS AND APPARATUS FOR UNDERWATER DRILLING OF OIL AND GAS WELLS The present invention relates to a method of and apparatus for underwater drilling of oil and gas wells and is particularly directed to drilling wells in deep water, i.e., in excess of 200 feet.

In current underwater drilling practice exploration wells are drilled from mobile drilling platforms or drilling barges. However in the case of production wells it 'upper ends of which open to the chamber, the well shafts being sealingly connected to the chamber, and an access shaft extending upward from the chamber for giving access to the chamber from above the water level.

Preferably the chamber has one or more removable water-tight hatches vertically aligned with the respective well shafts for providing access for a drill to each well shaft through the chamber.

According to a preferred feature of the invention, the chamber has attached thereto at least one vertically downwardly extending support for supporting the chamber in spaced relation to the water bed.

The invention further provides a method of drilling an underwater oil or gas well comprising securing an apertured guide platform at a predetermined distance above the water bed, passing well conductor pipes through an aperture or one of the apertures and into the bed, drilling the well through the conductor pipe and installing a well casing .within the pipe, attaching a well head unit to the upper end of the well casing just above the platform, attaching an upper portion to the platform to form therewith a chamber below the water surface which chamber encloses the well head unit, the upper portion having secured thereto an access shaft which extends upwards above the water surface, and pumping the water out of the chamber and access shaft.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which FIG. 1 shows an intermediate stage in the assembly of the apparatus,

FIG. 2 shows the apparatus just prior to completion of the assembly, and

FIG. 3 shows the assembled apparatus when in production and complete with quarters for maintenance personnel.

Referring first to FIG. 3 of the drawings, the apparatus is designed for use in the drilling of oil and/or gas wells under water and maintaining the well head equipment when the well or cluster of wells has been drilled and the oil or gas is flowing. The apparatus comprises a chamber having an access shaft 11 connected to it the upper end of which is disposed above the water surface level and a pile support 12 which in this instance is in the form ofa tube and is driven into the sea bed. A number of well conducting casings l3 driven into the sea bed are arranged about the support 12 and their upper ends project into the chamber. The apertures through which the conducting casings l3 and support 12 extend into the chamber 10 are provided with sealing means generally indicated at 13a and 12a of the type which are tightened against the tubes by hydraulic pressure, the interior of the chamber 10 and passage 11 being pumped free of water.

The gas or oil is led from well heads on the ugper ends of the conducting casings within the chamber 10 to a manifold M to which a flexible pipe 15 is con nected. The flexible pipe extends downward from its connection to the manifold to a pipeline 16 on the sea bed, and its suspended length is supported by cables 17 from one of the anchor cables 18 of the apparatus.

The upper portion 10a of the chamber and the access shaft 11 are separable from the lower portion 10b of the chamber and the support 12.

The apparatus is installed using a drilling rig, eg a rig which stands on legs on the sea bottom. The support tube 12 has welded to it, before being lowered into the water, one or more extensions (not shown) such that when the tube is lowered into the water its upper end is and remains above the water level 20- and can be operated on to hammer the tube into the sea bed. When the tube has been forced in to the sea bed an adequate distance eg ft. in clay or sandy soil or less in rocky soil, the support tube 12 is cut off at a level such that the lower portion 10b of the chamber can be lowered on toand secured, as by shims, at the correct height on the upper end of the tube 12.

The lower portion 10b of the chamber has apertures throughwhich the conducting casings 13 can be lowered and driven into the sea-bedby the rig. After each casing has been positioned the well is drilled within it in the conventional manner and a well head unit 23 is secured, with the assistance of divers, on the upper end of the well lining casing which is. just above the lower part 10b of the chamber so that the unit is housed within the chamber when the latter is complete.

When the cluster of wells has been drilled and the well head units secured, the assembly of the upper part 10a of the chamber and the access shaft 11 is floated into position above the wells For this purpose the access shaft is encircled by a buoyancy tank 25 which is internally partitioned by partition 25a to form several annular compartments. After the upper end of the shaft has been secured, selected compartments are flooded to bring the assembly into an erect position and the assembly is then lowered by the rig derrick on to the lower part of the chamber and decured. A sea] is disposed between the two parts of the chamber and is arranged so that hydrostatic pressure tightens the seal when the water is pumped out of the chamber and shaft. Sealed hatches 26 are provided in the upper wall of the chamber part 10a and in order to guide the upper .part of the chamber into its correct position on the lower part to align these hatches with the respective conductor casings for providing access for a drill to the conductor casings through the chamber, radially projecting rods (not shown) on oneof the parts are engaged in V-shaped slots (not shown) on the other part.

Anchor cables 18 are connected between the lower part 10b of the chamber and fixed heavy concrete anchorage blocks 27 on anchorage piles on the sea bed.

Additional anchor cables 28 may similarly be connected to the upper portions of the access shaft 11.

After the water has been pumped out of the chamber and access shaft, the well head units are coupled to the manifold M and the flexible pipe is installed and coupled to the outlet of the manifold to enable the oil or gas to be fed through the pipeline 16. Pumping out of the water tightens the seals between the conductor and support tubes and the lower part of the chamber and between the two parts of the chamber.

Subsequently a platform 29 is built on the upper end of the access tube and may support workshops for control and maintenance equipment, living quarters for the personnel, and a deck 30 to receive a helicopter. A travelling crane 31 may be supported from the deck 30.

The well head equipment can thus be serviced in atmospheric conditions. A staircase and lift are installed in the access shaft.

If necessary the chamber 10 and access shaft 11 can be flooded and the appropriate hatch or hatches 26 removed to give access to the drill-string to enable any of the wells to be re-worked. Thereafter the hatch or hatches can be replaced and-the chamber and access shaft pumped out again.

The chamber is disposed at a depth below the sea surface to avoid the effects of surface turbulence and sufficiently far above the sea bed to avoid the effects of scour. The depths concerned will vary with local conditions. The minimum height of the chamber above the sea bed will vary according to the tidal conditions. However the depth of the chamber below the surface will not exceed the depth at which a diver can conveniently work. In most cases the chamber will be at least ft. above the sea bed and not less than 120 ft. below the surface, so that the system is not intended for general use in water below 160 ft depth. However where conditions allowed it would be possible to install the invention in lesser water depths. Equally the apparatus can be used for drilling at greater depths, and in this case the chamber may be disposed a greater distance above the sea bed. For example in water up to 400 ft. deep the chamber may be placed up to ft. above the sea bed to enable the conductor pipes to be installed at a slight angle and to enable full advantage to be taken of divers assistance.

The bottom part of the chamber may contain one or more tanks for kill-fluid if desired.

The buoyancy tank may be pumped out to a selected degree to reduce or control the vertical loads on the support and can also be pumped out to permit the upper part of the chamber and all the upper works to be floated off and recovered in the event of abandonment of the wells or extensive workover functions.

The chamber is preferably spherical for maximum strength, the two parts being hemispherical, but other shapes may be adopted if desired.

I claim:

1. A method of drilling an underwater oil or gas well comprising the steps of driving a single vertical tubular pile into the water bed, the pile initially extending above the water level from the water bed and being operated on above the water level to drive it into the water bed, the upper portion of the pile being then cut off under water at a selected height above the water bed and removed, securing an apertured guide platform to the top of the remaining portion of the pile under water, which platform has at least one guide aperture therein arranged outwardly of the pile, passing a well conducting casing through said guide aperture and into the bed, drilling the well through the conducting casing, attaching a well head unit to the upper end of the casing just above the platform, permanently attaching an upper portion to the platform to form therewith a chamber below the water surface, which chamber encloses the well head unit, the upper portion hav ing secured thereto an access shaft which extends upwards above the water surface, and pumping the water out of the chamber and access shaft. 

1. A method of drilling an underwater oil or gas well comprising the steps of driving a single vertical tubular pile into the water bed, the pile initially extending above the water level from the water bed and being operated on above the water level to drive it into the water bed, the upper portion of the pile being then cut off under water at a selected height above the water bed and removed, securing an apertured guide platform to the top of the remaining portion of the pile under water, which platform has at least one guide aperture therein arranged outwardly of the pile, passing a well conducting casing through said guide aperture and into the bed, drilling the well through the conducting casing, Attaching a well head unit to the upper end of the casing just above the platform, permanently attaching an upper portion to the platform to form therewith a chamber below the water surface, which chamber encloses the well head unit, the upper portion having secured thereto an access shaft which extends upwards above the water surface, and pumping the water out of the chamber and access shaft. 